A Nitrate-Sensing Domain-Containing Chemoreceptor Is Required for Successful Entry and Virulence ofDickeya dadantii3937 in Potato Plants

Abstract

Nitrate metabolism plays an important role in bacterial physiology. During the interaction of plant pathogenic bacteria with its hosts, bacteria face variable conditions with respect to nitrate availability. Perception mechanisms through the chemosensory pathway drive the entry and control the colonization of plant host in phytopathogenic bacteria. In this work, the identification and characterization of the NIT sensor domain containing chemoreceptor of Dickeya dadantii 3937 (Dd3937) allowed us to unveil the key role of nitrate sensing not only for the entry to the plant apoplast through wounds but also for the infection success. We have determined the specificity of this chemoreceptor to bind nitrate and nitrite with a slight ligand preference for nitrate. Gene expression analysis showed that nitrate perception controls not only the expression of nitrate reductase genes involved in respiratory and assimilatory metabolic processes, but also the expression of gyrA, hrpN and bgxA, three well known virulence determinants in Dd3937.

Study of NIT domain‐containing chemoreceptors from two global phytopathogens and identification of NIT domains in eukaryotes

“…Considering that the ligand preferences differ between Dd15070‐LBD (Gálvez‐Roldán et al, 2022) and PscN‐LBD, we studied the NIT domain of the chemoreceptor ECA_RS02210 from P. atrosepticum SCRI1043. To this end, we used a similar approach and produced the individual domain as purified protein for its microcalorimetric analysis.…”

“…For example, maximal response for nitrate were 15‐fold higher than PacA‐mediated responses and 7‐fold higher compared to a strain in which the PacA concentration was increased by overexpressing its gene in trans ( Matilla, Velando, Tajuelo, et al, 2022 ) . The magnitude of nitrate chemotaxis was also superior to that mediated by the other characterised NIT‐containing chemoreceptor, Dd15070 of D. dadantii (Gálvez‐Roldán et al, 2022). The magnitude of nitrate response may indicate a particular physiological relevance.…”

“…Among the ligands tested were compounds with a structure very similar to nitrate/nitrite like phosphate, thiophosphate, dithiophosphate, sulphate, thiosulfate or tetrathionate, among others. Furthermore, the analyses of PacN‐LBD and Dd15070 (Gálvez‐Roldán et al, 2022) underline the nitrate/nitrite specificity of NIT domains. However, the failure of both ligands to bind to the NIT domain of P. aeruginosa chemoreceptor PA4520 indicated that not all family members bind these ligands.…”

“…The NIT domain of the Dd15070 chemoreceptor from Dickeya dadantii had a preference for nitrate and bound nitrite with lower affinity (Gálvez-Roldán et al, 2022). To assess ligand specificity and affinity of NIT domains, we have produced the NIT domain of the chemoreceptor PSA3335_RS14925 from P. savastanoi pv.…”

“…We have shown previously that the NIT domain of Pseudomonas aeruginosa chemoreceptor PA4520 does not bind nitrate/nitrite nor is it involved in mediating nitrate chemotaxis (Martín‐Mora et al, 2019). In contrast, another study showed that the NIT domain of chemoreceptor Dd15070 from Dickeya dadantii bound nitrate with an affinity that was only slightly superior to that of nitrite (Gálvez‐Roldán et al, 2022). NIT domains are found in more than 1% of chemoreceptors (Sanchis‐López et al, 2021), and the 3D structure of an apo‐NIT domain from the transcription anti‐terminator NasR has been reported (Boudes et al, 2012) (Figure 1).…”